Centrifuges by means of which sugar is centrifuged and with the aid of which the syrup flowing away can be thickened at the same time are already known from DE 123 174 B1 for example. These historical concepts have rotating sieve drums which are provided with screw-shaped blades at the upper or lower end faces thereof. Air is thus forced to pass through the sieve drums and thereby produce the desired evaporation process.
More modern continuously operating centrifuges, for centrifuging sugar massecuites are already known from CE 22 07 663 C3, CE 26 31 178 A1 or DE 38 28 204 C2 for example. Continuously operating centrifuges of this type, which are also designated as sugar centrifuges or continuous, centrifuges as catchwords, can be used in the cane sugar and sugar beet industries as well as in sugar refineries. They serve for mixing, distributing and accelerating the sugar massecuites that are being supplied thereto and thereby releasing the crystals from the syrup by means perhaps of a washing process involving the addition of water or steam.
The sugar massecuite is first supplied so a distributor pot serving as a feeding device. This is located in the axial region of the centrifuge and is intended so produce a distribution of the sugar massecuite which is as uniform as possible in the radial direction ready for further processing in the centrifuge. The massecuite is carried along in the distributor pot by adhering to the wall of the distributor pot and is thus gradually accelerated up to the peripheral speed of this wall. The massecuite is thereby distributed over the periphery of the distributor pot and is eventually spun-off over the upper edge of the distributor pot clue to the constant inflow of massecuite.
After covering a short stretch in free flight, the sugar massecuite strikes the inner surface of the product distributor which may also be referred to as an acceleration bell or a forerunner drum. During the free flight of the sugar massecuite, it is subjected to steam or wash-water issuing from corresponding feed lines.
Instead of or prior to being fed into a rotating distributor, the sugar massecuites could also be heated in a stationary, non-rotating element as is proposed in U.S. Pat. No. 4,052,304, whereby steam from the centrifuge is fed upwardly through the stationary element in the form of an eddy current. For this purpose, nozzle-like openings can be provided in the wall, of the stationary element.
The rotating product distributors in the centrifuges known from DE 22 07 663 C3 or DE 38 28 204 C2 for example are similar to a drum and flare-out slightly in the manner of a cone in the downward direction. At the lower periphery thereof, they form a discharge rim from which the sugar massecuites arriving there are spun off outwardly into the actual, conical, upwardly flaring sieve basket which rotates about the same vertical axis.
If the massecuite has a relatively high viscosity, it is prone to distribute itself unevenly and will form a layer of varying thickness on the inner surface of the product distributor. In order to counter this effect, it is proposed in EP 0 152 855 A3 that the peripheral wall of the product distributor should be subdivided into concentric ring elements of differing diameter that are arranged one within the other and thereby keep the spaces between the ring elements open in the upward and downward directions. Hereby, the ring elements should have a free upper and lower horizontal centrifuging rim in order to enable in this way the massecuites to be spun-off both above and below the respective ring elements.
Continuously operating centrifuges can be improved still more following a proposal in EP 0 487 780 B1. Continuously operating centrifuges utilising this concept have proved to be extremely satisfactory in practice and are widely used. Hereby, the product distributor is composed on the one hand of a plurality of mutually spaced, conically downwardly flaring ring elements, whilst on the other hand, the entire product distributor is surrounded by a downwardly flaring conical stationary bell which surrounds it with play on all sides.
In addition, the sugar centrifuges described in EP 0 487 780 B1 guide the sugar massecuites firstly into a distributor pot, and from there, to the first of the ring elements of the product distributor from where the sugar massecuites then move on to the next ring element, after moving across the annular gap, and finally they rise upwardly on the wall thereof due to the centrifugal forces operative on the sieve basket.
The individual ring elements are rigidly connected to one another by means of webs and accordingly rotate in synchronism. Apart from the webs, the annular gaps are free and thus make is possible for air to flow through the annular gaps in a direction that is approximately parallel to the ring elements, this thereby improving the process of homogenising the sugar massecuites which move radially outwardly in a direction perpendicular to the air flow whilst the air is flowing there through
The bell is stationary thereby enabling air and/or steam to be supplied from above into the region within the bell in a simple form.
In practice, there is considerable interest in making further improvements to precisely these proven and widely employed continuously operating centrifuges for centrifuging sugar massecuites.
Consequently, the object of the invention is to propose a continuously operating centrifuge of the type indicated in the Preamble of the main Claim which, enables such further improvement to be made,